AbstractThe effect offerrite–pearlite content on the cleavage fracture behaviour of carbon steels was determined via plain tensile tests at temperatures from 12 to−196°C. It was found that, under conditions of uniaxial tension within the test temperature range, the cleavage fracture stress for pearlitic eutectoid steel is independent of temperature, whereas that for mild steel changes with temperature and exhibits a depression at low temperatures. An increase in the proportion of pearlite enhances the effect of pearlite colonies as obstacles to cleavage crack propagation. Only when the volume fraction of pearlite is comparable to that of ferrite does the steel begin to display the fracture features of pearlitic steel. Possible mechanisms manifesting different fracture characteristics for steels of various ferrite–pearlite contents are discussed with the aid of fractographic observations.MST/1075